src/lib/config.c: fix setting cpuunits

Commit c167d55a075a2600fa5f42c1e9a1f1ebefd0abaa introduced regression:
`vzctl set VEID --cpuunits NUMBER` ignored. This fixes inability to set
cpuunits.

http://bugzilla.openvz.org/1369

[kir@openvz.org: formatting, extra {} brackets removed]
1 file changed